1. Field of the Invention
The present invention is directed to a method of manufacturing and a device used therewith with the method using photo-etching techniques to produce a micro-wiring arrangement on a flexible, insulating carrier band for the purpose of contacting semiconductor circuits in which the carrier band contains at least one opening for receiving an assembly and has at least one thin metal strip extending across the opening on one surface of the band.
2. Prior Art
In the manufacture of etched micro-wiring arrangements for the contacting of semiconductor circuits, it is well known to start with a flexible, insulating carrier band which has transfer perforations and openings to subsequently receive assemblies. Such a tape or carrier band is disclosed in U.S. Pat. No. 3,763,404. The carrier band or tape has a metal layer applied to one surface to form a laminated band and after the application of the metal layer, the laminated band is coated on both sides with a photosensitive varnish. The photosensitive varnish layer, which covers the metal layer and is the first layer, is then exposed through a corresponding photographic mask and developed so that it either produces a positive etching mask which exposes those portions of the metal layer which are to be etched away or produces a negative mask which is used during the applying of a final surface of etch resistant material such as by electrodeposition. When etch resistant material is applied to form the etching masks, the remaining portions of the first photosensitive varnish layer is completely removed to expose or uncover the portions of the metal layer which are to be subsequently removed. With the etching mask either being formed by the remaining portion of the first photosensitive varnish layer or being formed by the electrodeposited etch resistant material, the subsequent etching operation is performed to produce the desired wiring arrangement or circuit pattern. The photosensitive varnish layer, which is applied to the opposite side of the laminated band and is a second layer, is intended to protect during etching the portion of the metal foil or layer which extends across any of the openings such as those that receive the assembly and if the process includes the electrodepositing of the final surface layer, this layer also prevents the deposition of the etch resistant material on this portion.
When coating both sides or surfaces of the laminated band with the photosensitive varnish layers, inevitable differences in the thickness of the photosensitive varnish layers on each surface will occur and particularly the second layer on the other surface in the neighborhood of each of the openings in the band which are to receive the assemblies. This nonuniform layer thickness distribution presents problems during drying of the photosensitive varnish layers because either the thinner parts of the layers are overheated during drying and become brittle or the thicker parts of the layers are insufficiently dried. Photosensitive varnish layers, which have been rendered brittle, will lose their sensitivity to exposure. An inadequately dried photosensitive varnish will be dissolved by the developer even at the unexposed zones or portions. As soon as the second photosensitive varnish layer on the other surface is dissolved by the developer in the region of the assembly opening, a risk arises that the etching of the wiring structure circuit will produce unwanted removal of the metal strips of the metal layer which are to extend into or across the opening so that the desired wiring or circuit structure can no longer be produced with the proper shape or pattern. If, prior to etching, an electrodeposited final surface layer is applied on the exposed metal layer, then there exists a risk that unwanted deposition of metal will occur on the other surface on the position of the metal layer which extends across each of the openings so that during the subsequent etching step, the desired circuit or wiring arrangements will not be obtained. In addition to problems with unwanted removal of the second layer on the other surface during developing, similar problems will occur during the removal of the remaining portion of the first layer after the electrodeposition of the final surface. Thus, in order for the second layer on the other surface to perform its protective function during the etching operation, it cannot be dissolved during the step of removing the remaining portions of the first layer.